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package com.sun.mail.imap;

import java.util.Vector;

import javax.mail.*;

import com.sun.mail.util.*;
import com.sun.mail.imap.protocol.MessageSet;
import com.sun.mail.imap.protocol.UIDSet;

/**
 * Holder for some static utility methods.
 * 
 * @author John Mani
 * @author Bill Shannon
 */

public final class Utility {

	// Cannot be initialized
	private Utility() {
	}

	/**
	 * Run thru the given array of messages, apply the given Condition on each
	 * message and generate sets of contiguous sequence-numbers for the
	 * successful messages. If a message in the given array is found to be
	 * expunged, it is ignored.
	 * 
	 * ASSERT: Since this method uses and returns message sequence numbers, you
	 * should use this method only when holding the messageCacheLock.
	 */
	public static MessageSet[] toMessageSet(Message[] msgs, Condition cond) {
		Vector v = new Vector(1);
		int current, next;

		IMAPMessage msg;
		for (int i = 0; i < msgs.length; i++) {
			msg = (IMAPMessage) msgs[i];
			if (msg == null || msg.isExpunged()) // expunged message, skip it
				continue;

			current = msg.getSequenceNumber();
			// Apply the condition. If it fails, skip it.
			if ((cond != null) && !cond.test(msg))
				continue;

			MessageSet set = new MessageSet();
			set.start = current;

			// Look for contiguous sequence numbers
			for (++i; i < msgs.length; i++) {
				// get next message
				msg = (IMAPMessage) msgs[i];

				if (msg.isExpunged()) // expunged message, skip it
					continue;
				next = msg.getSequenceNumber();

				// Does this message match our condition ?
				if ((cond != null) && !cond.test(msg))
					continue;

				if (next == current + 1)
					current = next;
				else { // break in sequence
						// We need to reexamine this message at the top of
						// the outer loop, so decrement 'i' to cancel the
						// outer loop's autoincrement
					i--;
					break;
				}
			}
			set.end = current;
			v.addElement(set);
		}

		if (v.isEmpty()) // No valid messages
			return null;
		else {
			MessageSet[] sets = new MessageSet[v.size()];
			v.copyInto(sets);
			return sets;
		}
	}

	/**
	 * Return UIDSets for the messages. Note that the UIDs must have already
	 * been fetched for the messages.
	 */
	public static UIDSet[] toUIDSet(Message[] msgs) {
		Vector v = new Vector(1);
		long current, next;

		IMAPMessage msg;
		for (int i = 0; i < msgs.length; i++) {
			msg = (IMAPMessage) msgs[i];
			if (msg.isExpunged()) // expunged message, skip it
				continue;

			current = msg.getUID();

			UIDSet set = new UIDSet();
			set.start = current;

			// Look for contiguous UIDs
			for (++i; i < msgs.length; i++) {
				// get next message
				msg = (IMAPMessage) msgs[i];

				if (msg.isExpunged()) // expunged message, skip it
					continue;
				next = msg.getUID();

				if (next == current + 1)
					current = next;
				else { // break in sequence
						// We need to reexamine this message at the top of
						// the outer loop, so decrement 'i' to cancel the
						// outer loop's autoincrement
					i--;
					break;
				}
			}
			set.end = current;
			v.addElement(set);
		}

		if (v.isEmpty()) // No valid messages
			return null;
		else {
			UIDSet[] sets = new UIDSet[v.size()];
			v.copyInto(sets);
			return sets;
		}
	}

	/**
	 * This interface defines the test to be executed in
	 * <code>toMessageSet()</code>.
	 */
	public static interface Condition {
		public boolean test(IMAPMessage message);
	}
}
